It is the long range plan of this project to evaluate actions of receptors for toxic halogenated aromatics and estrogenically-active chemicals in relation to hepatotoxic potency of these compounds. These studies focus on receptor mediated effects on gene expression critical to tumor promotion using the rat two-stage model. The compounds of special interest are 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), structurally-related chlorinated dibenzodioxins and bibenzofurans, diethylstilbestrol, ethinylestradiol and Alpha-zearalonal. The goals of these studies are to quantify the amount of occupied receptor (chronic exposure) necessary to produce a specified risk of liver tumors in rats that had been treated previously with an initiating agent.